La Manzana de las Luces

Address Perú 222, San Telmo/Microcentro

"The Block of Lights" — a colonial complex at the corner of Perú and Alsina streets that was the intellectual centre of Buenos Aires from the early colonial period through the 19th century. The block held the first Jesuit church, the first school, the national archive, and (briefly) the first printing press in Argentina.

The complex is now a cultural centre, with guided tours that include the colonial buildings and a section of the 18th-century tunnel network beneath. The tunnels are the main draw — roughly four metres below street level, brick-vaulted passages that run for over five kilometres under the old city, though only a short section is accessible to the public. Tours depart on weekend afternoons; book through the website.

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A story
The tunnels under La Manzana de las Luces were dug by the Jesuits in the early 18th century and extended over several decades. Their exact purpose has been debated: they may have served as escape routes, as storage, or as communication passages between the Jesuit properties. When the Jesuits were expelled from Buenos Aires in 1767, the tunnels were sealed; they were only rediscovered and partially mapped in the 20th century. Some tunnels still connect to buildings several blocks away.